The present invention is in the field of valves and is more particularly directed to a new and improved expanding gate valve.
Expanding valves, and particularly expanding gate valves employing a gate movable into a cut-off position with portions of the gate then moving outwardly in sealing contact with the body of the valve, have been well known for many years as exemplified by prior U.S. Pat. Nos. 153,561; 408,706; 681,285; 983,960; 1,023,955; 1,057,226; 1,057,308; 1,250,041; 1,391,987; Re. 20,101; 2,326,988; 2,655,339; 2,793,831; 2,863,629; 2,986,371; 4,189,127; 4,193,577; and 4,231,440.
Prior known expanding gate valves have suffered from a number of defects and shortcomings for which the present invention provides a solution. For example, many of the prior known expanding gate valves have been extremely complicated in construction so as to be difficult and expensive to manufacture and maintain. Other valves have not proven to be functionally adequate to handling high-pressure valving operations such as in pipe lines and the like with one particular problem arising from the fact that lubricating grease employed in many of the prior valves is contaminated by the liquid being pumped and is frequently discharged into the flow through the valve so as to impair the lubrication of the movable valve components to render them difficult or impossible to operate and to also create a substantial likelihood of mechanical failure. Also, many prior valves do not provide an unobstructed path of movement as is necessary for the passage of cleaning pigs or other implements through the valve.
Therefore, it is the primary object of this invention to provide a new and improved expandable gate valve.
Achievement of the foregoing object is enabled by the preferred embodiment through the provision of a valve body consisting of three sections comprising an intermediate section sandwiched between two outer body sections with the intermediate section including a gate chamber in which a gate is mounted for reciprocation by a threaded main stem member. The intermediate valve section also includes camming surfaces on a central gate block positioned between seal blocks of a movable gate. The camming surfaces cooperate with roller followers engaged with camming surfaces on the seal blocks so that transverse relative movement of the central gate block with respect to the seal blocks effects outward movement of the seal blocks into sealing contact with seal members provided in the valve body adjacent the ends of flow passageways through which liquid would normally flow absent the presence of the gate in its closed position. The gate also includes a gate conduit alignable with the flow passageways in the valve body for permitting flow through the valve when the gate is moved to its open or non-blocking position. When the gate is in its closed position, conduit seal plates completely cover the ends of the gate conduit to prevent grease or other lubricant in the valve body from entering the gate conduit when the gate is in its closed position so as to be entrapped by the liquid flowing through the gate conduit upon its return to the open position. Thus, the loss of lubricant is effectively and efficiently precluded in a novel manner.
Outward movement of the seal blocks of the gate is quickly and effectively provided by rotation of a cam drive stem extending coaxially along the length of the main stem which has right and left hand thread sections engageable with different portions of the gate to effectively reciprocate the camming means relative to the seal block members so as to rapidly cause outward movement of the seal blocks to provide a complete seal against fluid flow through the valve.
In a second embodiment, the roller bearings are eliminated and simple inclined plane camming surfaces are used with the second embodiment being less expensive to manufacture and being completely satisfactory in operation for lower pressure installations. A third embodiment employs single inclined plane camming surfaces for moving the seal blocks outwardly.
A better understanding of the preferred embodiments of this invention will be achieved when the following detailed description is considered in conjunction with the appended drawings in which like reference numerals are used for the same parts as illustrated in the different figures.